Large screen displays or multi-element lighted displays for the presentation of time-dependent images such as videos have become more common in recent years. Many such displays are used in fixed locations such as at sporting grounds, or in temporary locations for special events such as at concerts or large public gatherings. Multi-element lighted displays are also commonly used as indicators on printed circuit board (PCB) assemblies.
PCBs, for use in computers and other electronic assemblies, include many light sources, typically light emitting diodes (LEDs). It is common practice to test circuits and components of a PCB assembly, including display elements, by routing signals from light detection elements that detect the light emitted by the display elements to a test fixture. Test signals are applied to the PCBs, and voltages generated across the various components and key parts of the circuit are monitored for verifying the operational characteristics of the components and the circuit. Though this method can provide high throughput in testing of display elements, it can be very time consuming and expensive when the number of displays is large, particularly when multiple PCBs are tested at the same time. In particular, the amount of data to be analyzed can be large for a display utilizing multiple light emitting elements.
Other types of automatic vision testing systems, which test for both the electrical and optical characteristics of LEDs on a printed circuit board are also available. Typically, such vision testing systems rely on a video camera and a frame grabber. The video camera images the printed circuit board, and the frame grabber grabs an image of the printed circuit board when the LEDs are powered up. The image is subsequently processed and interpreted by a computer. However, such automatic vision testing systems tend to be relatively expensive, relatively large, and unwieldy. Additionally, because the image of the printed circuit board grabbed from the video camera contains a significant amount of redundant information, relatively sophisticated algorithms and relatively large amounts of computer processing power are required to extract the relevant data from the image to verify that the LEDs are operational.
While it is common to employ a variety of other optical testing methods such as advanced imaging techniques using infra-red cameras, these methods can suffer from scalability issues because of angle-of-view considerations for multiple PCB assemblies, and because of the physical room/layout of multiple PCB assemblies. Such optical testing methods of display elements on PCBs or PCB assemblies are far from error proof, and miscalculations and undetected faulty devices could be harmful in certain situations, for example, if a user relies on an LED mounted on a PCB configured to indicate excessive applied voltage to a circuit or a circuit component, and if the failure of the LED is undetected, significant damage could be potentially caused to the circuit and/or the user.
PCB assemblies with display elements are often tested by routing signals from photodetectors to test equipment or using high-resolution cameras and computer vision. Large displays with high definition and resolution have a higher number of densely packed LEDs. As a result, testing such large displays can be quite complex. Moreover, if a single element of a multi-element display fails, the whole PCB assembly is rejected and sent for rework. Additionally, testing a large number of LEDs requires an enormous amount of computing resources and can be very time consuming.
The disclosed system and methods for testing multi-element lighted displays, address one or more of the problems set forth above and/or other deficiencies in the prior art.